1. Field of the Invention
This invention relates to a latch and more particularly a door latch of the type having a fixed mounting on a door and a latch operating handle carrying a lock whereby the handle may be locked to the mounting when the door is latched.
2. Description of the Prior Art
Vehicles such as vans, trucks or the like are provided with a door which permits entrance into the vehicle or restricted portion thereof. A handle located on the outside of the vehicle moves to operate a latch mechanism within or behind the door to latch the door closed or unlatch it for opening. To lock the latch mechanism, typically a key-operated lock within the door is locked to prevent the latch mechanism from being operated by the handle. Alternatively, a lock may be provided in the handle to lock the handle to the door when latched closed. Anyone desiring to open the door must have the proper key and must first unlock the lock and thereafter operate the handle to unlatch the door.
A drawback heretofore observed in the use of these latch-lock systems is that of changing the lock. It is sometimes desirable to be able to change the lock and thereby assure the security of the interior of the vehicle should the key to the lock fall into the wrong hands. Accordingly, U.S. Pat. No. 4,380,915 entitled "A Latch Having a Removable Lock" and assigned to the assignee of this application sets forth a means whereby the lock can easily be changed.
However, it has been found that latches of the type having a removable lock can lock the door closed without the presence of the key to the lock. Often locking is accomplished merely by pushing the lock to its locked position either with or without the key being inserted into the lock. This sometimes leads to the perplexing problem wherein the key is inadvertently left within the vehicle, the door is closed and latched and the lock is pushed to its locked position. In turn, this leads to the inability to re-open the door since the keys are locked inside or, if the ignition key to the vehicle is on the same keychain, the inability to drive the vehicle. Heretofore the only solution suggested was to provide a set of identical keys to be produced when the keys in the possession of the driver are locked within a vehicle. This necessitates, for fleets of vehicles, the maintenance of a large inventory of alternate keys and the problem of how to deliver the alternate keys to the driver for opening of the door.
It is an object of this invention to set forth a latch having a removable lock which cannot be locked without the use of the key.